interregnum

Etymology

Learned borrowing from Latin interrēgnum, from inter- (prefix meaning ‘between’) (ultimately from Proto-Indo-European *h₁entér (“between”)) + rēgnum (“reign; royal power”) (nominalized from the neuter of *rēgnus, from rēx (“king; ruler”, oblique stem rēg-) + -nus (suffix forming adjectives), ultimately from Proto-Indo-European *h₃reǵ- (“to righten; to straighten”)). The plural form interregna is a learned borrowing from Latin interrēgna.